Control Flow

if and else

They are the same. But Kotlin support also if-else expression

while and do-while, break and continue

They are the same: for Dart see here. For Kotlin see here

for loops

standard loop

Kotlin

//standard for loop    
for (i in 1..3 step 1) {
    println(i) //1 2 3
}

//standard for loop: step 1 can be omitted
for (i in 1..3) {
    println(i) //1 2 3
}

//standard reversed loop (note that the step is POSITIVE!)
for (i in 6 downTo 0 step 2) {
    println(i) //6 4 2 0
}

//standard reversed loop: step 1 can be omitted
for (i in 6 downTo 0) {
    println(i) //6 5 4 3 2 1 0
}

Dart

//standard for loop    
for (var i=1; i<=3; ++i) {
    print(i); //1 2 3
}

//standard reversed loop
for (var i=6; i>=0; i-=2) {
    print(i); //6 4 2 0
}

loop variable captured in closure

Kotlin

//Closures inside of Kotlins’s for loops capture the value of the index
var callbacks = mutableListOf<()->Unit>()
for (i in 0..2) {
  callbacks.add({ println(i)})
}
// print 0 and then 1
callbacks.forEach{ c-> c() }

Dart

//Closures inside of Dart’s for loops capture the value of the index
var callbacks = [];
for (var i = 0; i < 2; i++) {
  callbacks.add(() => print(i));
}
// print 0 and then 1
callbacks.forEach((c) => c()); 

loop over iterable

For Dart see iteration in library-tour. For Kotlin see for loops and iterable in stdlib

Kotlin

var cities = listOf("Rome","Paris","London")
//iterate over elements of iterable
// the same as in Dart see 
// see also 
for(city:String in cities) //the String type annotation can be omitted
{
    println(city)    
}

Dart

  //iterate over elements of iterable
//see 
var cities=["Rome","Paris","London"];
for(final city in cities) //instead "final" we can specify "var" or the explicit type (String)
{
    print(city);    
}

iterable.forEach()

For Dart see forEach. For Kotlin see forEach in stdlib

Kotlin

//iterable has also a forEach method for iterating over the elements
cities.forEach { city-> println(city) }

//or more simply
cities.forEach{ println(it) }

Dart

//Iterable classes also have a forEach() method as another option:

cities.forEach((city) {print(city);});

//or more simply
cities.forEach(print);

switch and case

For Dart see switch and case. For Kotlin see when expression.

Kotlin

var job = "nodejs dev";
val onJavascriptDev = { println("a Javascript dev") }
when (job) {
    "nodejs dev" -> {
        println("a  nodejs dev")
        onJavascriptDev(); //no support to jump to another label like in Dart
    }
    "frontend dev" -> {
        println("a frontend deb");
        onJavascriptDev() //no support to jump to another label like in Dart
    }
    "android dev", "iOS dev" -> println("A mobile dev")
    "javascript dev" -> onJavascriptDev()
    else -> println("Unknown job")
}

Dart

var job='nodejs dev';
switch (job) {
  case 'nodejs dev':
    print("a  nodejs dev");
    continue javascript_dev;
  case 'frontend dev':
    print("a frontend deb");
    continue javascript_dev;
  case 'android dev':
  case 'iOS dev':
    print("A mobile dev");
    break;
  javascript_dev:    
  case 'javascript dev':
    print("a Javascript dev");
    break;
  default:
    print("Unknown job");
}

case fall-through is prohibited

Only empty case fall-through is allowed. Dart requires break at the end of each case . Other valid ways to end a non-empty case clause are a continue (continue execution to another clause), throw, or return statement.

overriding == for compared object is prohibited

Dart does not allow classes for objects that are compared in a switch statement to override operator==

assert

in Dart Debug mode use assert(condition, optionalMessage) to disrupt normal execution if a boolean condition is false.

In Kotlin assert is supported for JVM and Native platforms;

Kotlin

// Make sure the variable has a non-null value.
assert(text != null)

// Make sure the value is less than 100.
assert(number < 100)

// Make sure this is an https URL.
//To attach a message to an assertion, add a string as the second argument to assert
assert(urlString.startsWith("https")){"URL ($urlString) should start with \"https\"."}

Dart

// Make sure the variable has a non-null value.
assert(text != null);

// Make sure the value is less than 100.
assert(number < 100);

// Make sure this is an https URL.
//To attach a message to an assertion, add a string as the second argument to assert
assert(urlString.startsWith('https'),'URL ($urlString) should start with "https".');